Checks for an Update for a Spigot Plugin using a pom.xml file from a public repository defined within the URL. Ensure it's a raw.githubusercontent url...

UpdateChecker.java

import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;

import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;

public class UpdateChecker {

	String url = "https://raw.githubusercontent.com/AkaGiant/SimpleExp/dev/pom.xml";

	double current = Double.parseDouble(
		SimpleExp.getPlugin().getDescription().getVersion()
			.replaceAll("[^\\d.]", "").trim()
	);
  
	double latest = 0.0;

	public void run() {
		this.latest = getGithubLatest();

		if (this.latest == -1) return;

		if (current > latest) {
			Logger.toConsole("&fYou seemingly have a newer version than is currently released");
			Logger.toConsole("&fCurrent: &b" + current + " &8| &fLatest: &c" + latest);
			Logger.toConsole("&m------------------------------------");
			return;
		}

		if (current == latest) {
			Logger.toConsole("&aNo Updates Found");
			Logger.toConsole("&fCurrent: &b" + current + " &8| &fLatest: &c" + latest);
			Logger.toConsole("&m------------------------------------");
			return;
		}

		Logger.toConsole("&aUpdates Found");
		Logger.toConsole("&fCurrent: &b" + current + " &8| &fLatest: &c" + latest);
		Logger.toConsole("&fURL Will be provided soon.");
		Logger.toConsole("&m------------------------------------");
	}

 	private double getGithubLatest() {
	    InputStream in = null;
	    try {
		    in = new URL(url).openStream();
	    } catch (IOException e) {
		    Logger.severe("&fUnable to check for updates!");
	    }

	    NodeList nodeList;

	    try {
		    nodeList = DocumentBuilderFactory.newInstance().newDocumentBuilder().parse(in).getElementsByTagName("version");
	    } catch (SAXException | IOException | ParserConfigurationException e) {
		    Logger.severe("&fUnable to get and find the Version identifier for the latest version.");
			  return -1;
	    }

	    String latestVersion = nodeList.item(0).getFirstChild().toString().replaceAll("[^\\d.]", "").trim();
	    return Double.parseDouble(latestVersion);
    }
}